Apparatus for reading from or writing to optical recording media having a tilting-compensation device

1. An apparatus for reading from or for writing to optical recording media comprising an optical scanner comprising: a light source for generating a light pencil; focusing means for focusing the light pencil; a tilting-detection device for detecting tilt; and a tilting-compensation device for compensating tilt, wherein the tilting-detection device comprises an optical grating for influencing the light pencil, a detector element for detecting the influenced light pencil, a first control device for controlling the light source and the focusing means and a second control device for controlling the tilting-compensation device in response to an output signal of the detector element, wherein a grating constant d of the optical grating is related to a wavelength of the light source and numerical aperture NA by the relationship d k* /NA, where the proportionality factor k assumes the value k 1.2 10%.

2. The apparatus according to claim 1 , further comprising a positioning unit for positioning the optical grating parallel to a reference area of the apparatus.

3. The apparatus according to claim 2 , further comprising a drive device for moving the optical grating parallel to the reference area of the apparatus.

4. The apparatus according to claim 3 , wherein the optical grating has optical properties corresponding to optical properties of the optical recording medium.

5. The apparatus according to claim 4 , wherein the optical grating is a two-dimensional grating.

6. The apparatus according to claim 1 , further comprising a drive device for moving the optical grating parallel to a reference area of the apparatus.

7. The apparatus according to claim 1 , wherein the optical grating is a two-dimensional grating.

8. In an apparatus for reading from or for writing to optical recording media, a method for compensating for the tilting of an optical element, comprising the steps of: introducing an optical grating into a beam path following the optical element, activating a light source, varying a focal point of the beam path on the grating in a direction non-parallel to a grating plane, detecting intensity of the light coming from the grating, determining a contrast between minima and maxima of the detected intensity, varying the tilting of the optical element until the contrast is at a maximum, and maintaining the set tilting associated with the maximum contrast.

9. The method according to claim 8 , further comprising the step of: orienting the grating in a normal plane to the desired direction of the optical axis.

10. The method according to claim 9 , characterized by the following additional step: varying the position of the grating in the grating plane in a direction crossing the grating lines.

11. The method according to claim 10 , further comprising the steps of: rotating the grating with the optical axis as axis of rotation, varying the tilting of the optical element until the contrast is at a maximum.

12. The method according to claim 9 , further comprising the steps of: rotating the grating with the optical axis as axis of rotation, varying the tilting of the optical element until the contrast is at a maximum.

13. The method according to claim 8 , further comprising the step of: varying the position of the grating in the grating plane in a direction crossing the grating lines.

14. The method according to claim 8 , further comprising the steps of: rotating the grating with the optical axis as axis of rotation, varying the tilting of the optical element until the contrast is at a maximum.